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Current Limit Circuit

Jay Carlo De Claro
Prodigy 160 points
Other Parts Discussed in Thread: OPA170, LM321, OPA237

Hi All,

I have a circuit that will limits current and I set to 150mA maximum based on my design, I need to charge a huge capacitor 8mF with this 150mA, I need 5A current with a duty cycle of 4% on R1(R1 is an active load that consume 5A in span of 200uS with a period of 5mS), This 28V will dip once the switch is ON with 200uS(as normal), This is my application that I want to add this current limit circuit.

When I simulate this circuit I can limit the current to 150mA which is good but once I prototype it Headache arises, I always use OPA170 Opamp for my prototype but I cannot get any success on this this OPAMP which always got damage, Once I increase the current more than 150mA, Is there any problem with my OPAMP selection? If so can you recommend any OPAMP that is suitable with my application. Or is there any problem with the circuit. I found the circuit on this site 

electronics.stackexchange.com/.../active-current-limiter

I am hoping some help from expert/s.

Thanks and regards,

Jay

  • 0
    Prodigy 160 points

    Hi All,

    Interestingly OPA237 on my simulation using TINA is not working but OPA2234/LM321/OPA234 is working on TINA SPICE using this circuit.

    I am now purchasing LM321 and OPA234 and OPA2234 and I will try again on bench.

    I am just wondering why the OPA237/OPA170 are not working on bench/prototype which is the same as my simulation. Which OPAMP parameters matters for this kind of circuit why these OPA2234/LM321/OPA234  opamp are working.

    Appreciate your input.

    Thanks and regards,

    Jay

  • 0 in reply to Jay Carlo De Claro
    TI__Guru**** 151776 points
    Jay,

    I can speak on the LM321. It should not work because the input pin voltage are too close to the VCC of the op amp.
    A rail to rail input or a input to positive rail op amp is needed.

    I also have to ask, why 150mA? 4% of 5 amps is 200mA.
  • 0 in reply to Ron Michallick
    Prodigy 160 points

    Hi Ronald,

    I have a boost switcher that boost 28V I used this IC (TPS61170DRVR) that's why I need to limit to 150mA only because my switcher cannot give me more than that.

    How about the other 2 opamp that I choose?

    Can you recommend TI opamp that I can used?

    Appreciate if you can suggest one.

    Thanks and regards,

    Jay